Well, I picked up my brand new Benelli M4 earlier today. I disassembled it and lubed it up.
I took a 100 rounds of bird shot 2 and 3/4 shells out. Plus a couple dozen buckshot shells and slugs.
Got thru about 75 rounds and experienced some failures to feed.
A couple rounds later, a complete failure. A round simply would not feed. Upon closer inspection, there was a small rod jammed between the round and the top of the receiver.
This rod was one of the gas pistons!

I'm extremely pissed. 1300 bucks, and the gun busts under a 100 rounds down the tube.
Now I have to deal with customer service and see how they want to handle it.
-Steve

Quoted: I'm extremely pissed. 1300 bucks, and the gun busts under a 100 rounds down the tube. Now I have to deal with customer service and see how they want to handle it. -Steve

That Sucks

But it's not typical of Benelli , I have an M1-90 that I bought used . I broke the base of the
rear sight when it fell off a bench . I called customer service to find a factory service center
because it messed up the screw hole . The woman on the phone said she would have it covered
under warranty if I sent it to them , even though I wasn't the original owner .

It was a 3 week turnaround , and when I got it back the RO said they replaced the receiver, bolt
rear sight  .........  No Charge !

Crap!  Stevenb, did the gas piston break off (metal failure) or did it become detached from the rest of its assembly?  Not familiar with the design, so this may be a stupid question.

Quoted: A round simply would not feed. Upon closer inspection, there was a small rod jammed between the round and the top of the receiver. This rod was one of the gas pistons!

Where exactly was the rod portruding? Above or below the chamber?
And are you sure you reinstalled the pistons correctly?

Just spoke with Benelli USA. Not overly helpful, I have to send the busted piston into them so they can look it over. No big deal.
Here is a picture of the busted piston.


The piston is fairly easy to remove from the firearm. Actually there are two of them. From the picture above, the piece that broke off is the portion that extends thru the receiver and impacts on the bolt during the impingment.
I'm pretty sure it broke within the first 20 or 30 rounds. The weapon became sort of slugish, I could feel the action working. When I looked into the weapon, I could see nothing wrong because the piston was still free floating in place. Only when it made its way into the receiver did it cause a major failure.
Basically, the weapon was running off one piston for 20 rounds or so. It would probably even work still, not recommended though.
I did not remove the pistons from the barrel when I first received it. I simply lubed it lightly along with the rest of the shotgun before taking it out.
The gas pistons only move about a quarter inch during their travel. There is a shelf the shoulder hits on the barrel to keep it from protruding too far.  Where that shoulder is, and the piece that impacts on the bolt face meet is where it sheered.
I rechecked how many rounds went down range. I shot about 50 or so. Most were 2 & 3/4 bird shot loads at 3 dram. Definately not some shoulder busters.
Looks like my brand new shotgun is out of commission for at least a few weeks. Not pleased at all.
Those of you who have the M4, what the hell does the 273j, 274j & 275j parts listed in the gas system on page 16 of the spare parts manual? I can't disassemble that part, I hope all those pieces are in there.

-Steve

Edited to add:
The piece of the piston was above the feeding round when it caused the complete failure.

A little more info:
The rod that broke was the left hand side from looking down on the weapon (Inner receiver wall.)

I closely looked at the other piston, and there appears to be no sheering effects like the one that broke. You can sort of tell in the picture that there are now fracture rings around the piece that broke off. It is possible that this happened when it entered the receiver and got mashed by the bolt, but highly unlikely.
The steel looks very brittle in my opinion.
-Steve

Looks like the metal used in the piston construction had a flaw.

Sorry to hear about your M4. I certainly hope Benelli makes it right. Personally, I'd send the whole gun back to make sure there is nothing else wrong.

Stevenb,

Looks like there is very little transition between the adjacent flange and the part that broke off, i.e. a stress concentration there.  I'm unfamiliar with the significance of the rings above the fracture.  Been out of engineering too long.

See my post on the Benelli board.  See if they'll appease you by throwing in an M4 recoil tube, too.  If anybody can do it, they can.  And if ever there was a time to ask, now would be it.  Hell, even if they sold it to you for cost, at least make it available!

Quoted: Stevenb, See if they'll appease you by throwing in an M4 recoil tube, too.  If anybody can do it, they can.  And if ever there was a time to ask, now would be it.  Hell, even if they sold it to you for cost, at least make it available!

Good point, I'll continue to raise hell.
I'm trying to get them to pay for my shipping of the weapon to them.
-Steve

Quoted: I did not remove the pistons from the barrel when I first received it. I simply lubed it lightly along with the rest of the shotgun before taking it out.

I'm not sure what you are saying, but it specifically says in the owner's manual NOT to lubricate the pistons. They are to remain COMPLETELY dry.

EDIT: Oh yeah, I'm sorry to hear about your breakage. Hopefully you will get it all lined out soon enough.

What I ment by lightly lubing is applying a dry coating of oil to protect the metal from rusting.
Plus, I never had a chance to touch the gas pistons before it broke.
They don't want oil in the gas system because it collects debris, and simply splatters about needlessly.

Plus, I was only using the Benelli oil on the firearm at the time. I seriously hope that this weapon isn't that finicky. If it is, I'll probably be selling it as soon as it is fixed.
-Steve

Never heard of this before. Given the reputation this thing has, I'm going to attribute the breakage to a metallurgical flaw. I think Madness, here, ran his thoroughly & it gave him no problems. Replace that piece & I bet you'll be up & running.

Quoted: You could pick up a 870 Express while you are waiting for your B-gun to return from the shop. MIKE

You don't know how close you are to the truth.

I think I'll swap the piston with Benelli and run the gun to death. If problems arise, it's going back to them to replace. Unless I can talk them into swapping the recoil spring housing, then the gun is going there ASAP. It would be worth the hassle then.
I'm seriously doubting that they will play ball with me though.

Any of you guys find the safety to be extremely difficult to manipulate? I took out the trigger group and lightly lubed it to try to get it to loosen up some, but it is still very stiff. I've been playing with the button to try to break in the spring some.
The trigger pull isn't too bad. It's a little stiff, but it breaks very clean. The sights are dead nuts. My first round sent a soft ball flying.

What about this, what are the chances the other piston is vulnerable to the same problem? Could this be a bad batch of pistons?
-Steve

Ouch, did the rod breaking screw up the piston bore?

Quoted: Quoted: You could pick up a 870 Express while you are waiting for your B-gun to return from the shop. MIKE You don't know how close you are to the truth. I think I'll swap the piston with Benelli and run the gun to death. If problems arise, it's going back to them to replace. Unless I can talk them into swapping the recoil spring housing, then the gun is going there ASAP. It would be worth the hassle then. I'm seriously doubting that they will play ball with me though. Any of you guys find the safety to be extremely difficult to manipulate? I took out the trigger group and lightly lubed it to try to get it to loosen up some, but it is still very stiff. I've been playing with the button to try to break in the spring some. The trigger pull isn't too bad. It's a little stiff, but it breaks very clean. The sights are dead nuts. My first round sent a soft ball flying. What about this, what are the chances the other piston is vulnerable to the same problem? Could this be a bad batch of pistons? -Steve

Again, this is the first time I've ever heard of this happening. IMO, insist that Benelli replace both piston rods, not just the one that broke. After all, in a worst-case scenario, they both could have come from a bad batch. Remember - you're the customer. Don't capitulate if they seem stand-offish about your concern for wanting to have the product perform as advertised. Don't ask. Insist - politely, of course. Replacing both piston rods is a minor task, so they shouldn't get upset. Just do it.

As far as the controls are concerned, I've only handled the M1014. The sights, trigger, & even the PG were simply the best I've ever handled on SG - & I've handled & shot quite a few. I was even pleasantly surprised by the cheek weld afforded by the skeleton/collapsible stock. I expected it to be adequate, but it was as good as any full stock I've tried. I specifically remember the less-than-stellar write-up it received in "SWAT" mag, particularly in regard to the location of the stock's release button, which it was said could be accidentally engaged by the shooter's cheek when aiming. I noticed the button is recessed & not just sticking out there, & when I intentionally tried to push the stock against my face & aim, I couldn't depress that button. I also recall that the location of the safety was also criticized, but then, by way of comparison, the article heaped praise on the M1, which has an identical safety. Go figure. Once again - it worked for me.

In sum: it handled great for me. Just need to go shoot it. Hope it comes in soon.

The placement of the controls are fine to me, just the safety is very hard to press. Meaning it takes more preasure to take off the safety then it does to pull the trigger.
I would have prefered a slightly larger bolt release, like the one GG&G makes.

The gas pistons in mine seem to be free floating. Meaning, if you have the bolt locked to the rear, and you tip the weapon fore and aft, you can hear the pistons sliding back and forth. When the bolt is in battery, no noise is heard because the free play is removed since the bolt is resting up against the pistons.
Still unknown what the springs inside the front end of each gas cylinder is for. My only idea is that this is the part which is the auto regulating portion. Preasures over a set amount are vented out the front and under the hand guards while the pistons only require a set amount to cycle the action.
Or it may work the opposite way, the spring inside each piston waits until a specific amount of pressure build up is present, then it overcomes the spring load and impings the pistons to start the cycle.
The first is the most likely though.

From what I can see, the channel where the piston enters the receiver is in okay shape. You can tell something happened, but it appears to be only cosmetic. Just shinny edges around the channel.
Luckily for me the piece of the piston didn't end up in the barrel. Could of been real bad.
I really hate dealing with customer service. The guy I talked to today sounded as if he never even heard of a Benelli M4.
-Steve

I rarely, if ever, actually use the safety. I just keep my finger off the trigger.

Well, I finally got my replacement gas piston from Benelli today. Nearly a month after I sent the busted one in to them.
There was nothing in the package to explain what had happened, or even an apology.
It's raining cats and dogs today and tomarrow, so I doubt I'll make it out to put it through another exhausting test of 50 rounds of ball busting 2 and 3/4 birdshot, at 3 drams. If it doesn't break, I'll push it even further for maybe 150 - 200 rounds -- yeah, I'm a saddist like that.
Any more problems, and the whole gun is going back to them and I'm demanding a replacement. This BS with the batf and the collapsible stock is bugging me too. I don't care that much about the stock, but having the extended feed tube on it is importaint to me. If they keep it up, and give us all the finger, I may try to SBR it and get the 14" barrel entry variant. That way I'll be getting something back for the reduced capacity. My luck Benelli doesn't even sell that barrel to us pesants.
I'd really rather not deal with the SBR nightmare though.
I'm starting to have regrets about buying Benelli due to these issues. Unless someone steps up to the plate and starts offering American made parts to get the foreign part count down bellow 10 -- I don't see that a happening though.
If we could get companies like Vang comp to support this format, it might be doable and you might get some benefit too.
Anyone sit down and count out how many foreign parts are in the M4 as it is? I'm not certain which parts count.
-Steve

Quoted: I may try to SBR it and get the 14" barrel entry variant. That way I'll be getting something back for the reduced capacity.

IIRC, making it an NFA weapon (SBS) exempts it from 922(r) and you won't need to do the parts-count thing to add the mag extension or working telestock. You can then add all the evil features you want. Here in Indiana, we can have everything EXCEPT a SBS. Otherwise I would have already went that route, since I already own a MG and suppressors.

So, people could register their Benelli M4 as a SBS (Short Barreled Shotgun) and leave the standard length barrel on it and add all the evil they wish? Once a rifle is registered as a SBR, I don't think the law cares if you slap an upper with over 16" barrel on it.
I'd honestly rather have the added rounds and keep an 18.5" barrel.
The 200 dollar tax stamp isn't a big deal, but the 4 - 6 month wait time sucks. Then it is shaky about using the Class III weapon for self defense. That might be a wives tale I've heard though.
It may be the way for those of us in the "free" states to avoid the man kicking in our door.
-Steve